Meta-analysis of the performance variation in broilers experimentally challenged by Eimeria spp

Silymarin effectively prevents and treats Eimeria tenella infection in chicks

Silymarin, a botanical medicine derived from milk thistle seeds and is known to improve chicken growth and gut health when added to the feed. However, its role in the prevention and treatment of chicken coccidiosis remains unclear. This study investigated the efficacy of various doses of silymarin in preventing and treating Eimeria tenella infection in chicks. A total of 180 one-day-old specific pathogen-free chicks were randomized into six groups of 30 chicks each, no treatment (NC group); E. tenella infection (CC group); diclazuril medication during d 14 to 21 and E. tenella infection (DC group); and three groups infected with E. tenella and administered low, medium, or high doses of silymarin during d 12 to 21. All groups except NC were infected with E. tenella on d 14, with indicators observed on d 21. The growth performance was higher in the silymarin treated groups than that in the CC group, and the oocyst count per gram of manure, blood stool, and cecal lesion scores decreased. The medium-dose silymarin group exhibited the best treatment effect. Additionally, the silymarin groups displayed improved histological, morphology, and intestinal barrier integrity. The amounts of proinflammatory factors and harmful bacteria in the cecum were also reduced. Additionally, the activity of serum and cecal antioxidant enzymes, as well as the abundance of beneficial gut microbiota, increased in the cecum. In conclusion, this study demonstrated that silymarin can prevent and treat E. tenella infections. These data provide a scientific and conceptual basis for the development of a botanical dietary supplement from silymarin for the treatment and control of coccidiosis in chicks.

Comparing the effect of phytobiotic, coccidiostat, toltrazuril, and vaccine on the prevention and treatment of coccidiosis in broilers

This study compared 2 herbal anticoccidiosis drugs (water-soluble and feed-additive drugs) with monensin coccidiostat, toltrazuril (TTZ, anticoccidiosis drug), and Livacox Q (anticoccidiosis vaccine) in terms of their effects on the prevention and treatment of coccidiosis in broilers. In this study, 280 Ross 308 broiler chickens (a mix of both genders) were used in a completely randomized design with 7 treatments and 5 replications each including 8 chickens per replicate. On d 21 of rearing, all experimental groups, except for the negative control group (NC), were challenged with a mixed suspension of common strains of Eimeria, and the intended indices were assessed, including performance indices, number of oocysts per gram (OPG) of feces, intestinal injuries, and the total number of intestinal bacteria. In addition, the NC and the group receiving the monensin had greater body weight gain (BWG) (P < 0.05). At the end of week 6, the monensin group had the highest feed intake (FI), while the water soluble medicine treatment resulted in the lowest feed intake (P < 0.05). Regarding the lesion scores on day 28, the highest and lowest rates of jejunal injuries were observed in the positive control group (PC), the monensin and vaccine group respectively. The rate of oocysts excretion (oocysts per gram of feces = OPG) on different days was higher in the PC group, and the use of monensin could further reduce excretion compared to the other groups (P > 0.05). Based on a comparison of the population of lactic acid bacteria between the NC and both medicinal plant treated groups, the use of these products could increase the population of these types of bacteria. Moreover, the population of Escherichia coli was less considerable in the NC and herbal powder groups (P < 0.05). Overall, similar to commercial medicines, the herbal medicines used in this project can be effective in the prevention and treatment of coccidiosis and can improve profitability in broiler rearing centers by improving intestinal health.

Effects of a coccidiosis challenge on dietary methionine recommendations in broilers

Broilers are commonly exposed to coccidiosis infections, and the use of dietary strategies to reduce losses in growth performance has practical implications for the poultry industry. Methionine (Met) is typically the first limiting amino acid for broilers and is involved in metabolic and immunological pathways; however, literature is conflicting on how dietary Met requirements are affected by environmental stressors. Our objective was to assess how the Met requirement changes during coccidiosis based on results of growth performance, carcass traits, and health outcomes. Two trials were conducted using 780 male Ross 308 broiler chicks in floor pens randomly assigned to 1 of 12 experimental treatments. All birds received common starter (d 0-10) and finisher (d 24-35, Trial 2 only) diets, and only differed based on their assigned experimental grower diet (d 10-24). Trial 1 experimental grower diets ranged from 2.61 to 6.21 g/kg digestible Met. Trial 2 experimental grower diets were formulated to contain 15% below, at, or 15% above the Met requirement determined in Trial 1. Birds were exposed to a coccidiosis challenge on d 11, with blood and tissue collection (1 bird/pen) on d 18 and carcass processing on d 35 (2 birds/pen) in Trial 2. Data were analyzed using a 1- or 2-way ANOVA. A non-linear regression analysis was conducted in Trial 1 to determine the Met requirement of 4.32 g of digestible Met/kg of diet using BW gain. Coccidiosis infection reduced (P < 0.05) growth performance during the experimental grower and overall study periods in Trial 2. Increasing dietary Met from below requirement to meeting requirement during the grower period improved (P < 0.001) BW gain and feed conversion ratio (FCR), but this effect was only significant between treatments below and above the requirement for the overall study period. There was an interactive effect (P = 0.038) on FCR for the overall study period. These findings provide evidence that the Met requirement is likely increased during coccidiosis based on growth performance outcomes.

Coccidiosis in Egg-Laying Hens and Potential Nutritional Strategies to Modulate Performance, Gut Health, and Immune Response

Avian coccidiosis, despite advancements in management, nutrition, genetics, and immunology, still remains the most impactful disease, imposing substantial economic losses to the poultry industry. Coccidiosis may strike any avian species, and it may be mild to severe, depending on the pathogenicity of Eimeria spp. and the number of oocysts ingested by the bird. Unlike broilers, low emphasis has been given to laying hens. Coccidiosis in laying hens damages the gastrointestinal tract and causes physiological changes, including oxidative stress, immunosuppression, and inflammatory changes, leading to reduced feed intake and a drastic drop in egg production. Several countries around the world have large numbers of hens raised in cage-free/free-range facilities, and coccidiosis has already become one of the many problems that producers have to face in the future. However, limited research has been conducted on egg-laying hens, and our understanding of the physiological changes following coccidiosis in hens relies heavily on studies conducted on broilers. The aim of this review is to summarize the effect of coccidiosis in laying hens to an extent and correlate it with the physiological changes that occur in broilers following coccidiosis. Additionally, this review tries to explore the nutritional strategies successfully used in broilers to mitigate the negative effects of coccidiosis in improving the gut health and performance of broilers and if they can be used in laying hens.

Carbohydrases and Phytase in Poultry and Pig Nutrition: A Review beyond the Nutrients and Energy Matrix

This review aimed to clarify the mechanisms through which exogenous enzymes (carbohydrases and phytase) influence intestinal health, as well as their effects on the nutrients and energy matrix in diets fed to poultry and pigs reared under sanitary challenging conditions. Enzyme supplementation can positively affect intestinal microbiota, immune system, and enhance antioxidant status. Although enzymes have been shown to save energy and nutrients, their responses under sanitary challenging conditions are poorly documented. Immune system activation alters nutrient partitioning, which can affect the matrix values for exogenous enzymes on commercial farms. Notably, the carbohydrases and phytase supplementation under sanitary challenging conditions align with energy and nutritional valorization matrices. Studies conducted under commercial conditions have shown that matrices containing carbohydrases and phytase can maintain growth performance and health in poultry and pigs. However, these studies have predominantly focused on assessing a single level of reduction in energy and/or available phosphorus and total calcium, limiting our ability to quantify potential energy and nutrient savings in the diet. Future research should delve deeper into determining the extent of energy and nutrient savings and understanding the effects of alone or blended enzymes supplementation to achieve more specific insights.

Graded levels of Eimeria infection linearly reduced the growth performance, altered the intestinal health, and delayed the onset of egg production of Hy-Line W-36 laying hens when infected at the prelay stage

The aim of this experiment was to investigate how different levels of Eimeria infection affect the performance, intestinal health, oxidative status, and egg production of Hy-Line W-36 pullets and laying hens. Three hundred and sixty Hy-Line W-36 pullets, aged 15 wk, were randomly distributed into 5 treatment groups, each comprising 6 replicates and a nonchallenged control. At 15 wk, pullets were inoculated with different levels of mixed Eimeria species as high-dose, medium-high, medium-low, and low-dose treatments. The growth performance and average daily feed intake (ADFI) were measured from 0- to 18-days postinoculation (DPI), whereas hen day egg production (HDEP) was recorded from wk 19. The markers of gastrointestinal health and oxidative status were measured at 6 DPI, 14 DPI, and 23 wk of age. The findings revealed a significant linear reduction in growth performance in response to increased Eimeria challenge dosage on 6 and 14 DPI (P < 0.0001, P-L < 0.0001). An interaction between the graded level of Eimeria infection and DPI was observed for ADFI. The challenged pullets showed a reduction in ADFI starting at 4 DPI, which persisted until 14 DPI, when ADFI recovered back to normal. The most significant drop in feed intake was observed in 6 DPI in all the Eimeria-infected groups. The markers of gastrointestinal health (gastrointestinal permeability and tight junction proteins) were upregulated in challenged pullets because of infection, whereas the relative mRNA expression of key nutrient transporters was downregulated following infection on 6 and 14 DPI (P < 0.05). As a result of an infection on 6 DPI, the oxidative equilibrium was shifted toward the oxidative stress, and at the same time, upregulation of proinflammatory and inflammatory cytokines was observed (P < 0.05). An interaction between the Eimeria challenge dosage and bird age was observed for HDEP (P = 0.0427). The pullets infected with Eimeria started to lay eggs later than the Control birds. However, the HDEP of the challenged groups became similar to Control only at wk 22, 3 wk after laying eggs. In conclusion, coccidiosis reduced growth performance, altered gastrointestinal health, induced oxidative stress, and delayed egg production when infected at the prelay stage of pullets and negatively impacted the laying hens' overall performance.

Eimeria maxima infection impacts the protein utilisation of broiler chicks from 14 to 28 days of age

In floor-raised broilers, coccidiosis is responsible for reducing the use of nutrients, mainly by impairing intestinal tissue function and activating the immune system. Understanding and quantifying how balanced dietary protein (BP) is used when birds are challenged will allow nutritionists to make decisions regarding challenged flocks. This study aimed to determine the effects of Eimeria maxima on broiler performance and body composition, and to calculate changes in the maintenance and efficiency of protein utilisation (Ep). A total of 2 400 male 14-day-old Cobb500 broiler chickens were randomly allotted to ten groups with six replications of 40 birds each, with a 5 × 2 factorial arrangement of treatments. Five levels of BP in reference to digestible lysine (3.6, 7.2, 10.8, 14.4, and 18.0 g/kg) were fed to unchallenged (NCH) and challenged (CH) broilers with 7 × 103E. maxima sporulated oocysts from 14 to 28 days of age. Performance and body deposition were measured using a comparative slaughter technique to compare BP maintenance requirements and Ep. ANOVA followed by a posthoc test was performed to compare the effects of BP levels, challenge, and their interactions. A monomolecular model describing the responses of NCH and CH broilers to BP intake, maintenance, and maximum protein deposition was compared. There were significant interactions between body weight gain and digestible lysine intake among the factors studied. Infection had a negative impact on all variables analysed, proving the efficacy of the challenge. The maintenance did not differ between the CH and NCH groups. Increased levels of dietary BP did not recover the maximum protein deposition in CH broilers. Eimeria maxima significantly reduced Ep by a factor of 0.09 times on Ep compared to the control group. The Eimeria maxima challenge was responsible to modify the use of BP altering the body composition and impairing broilers performance.

Coccidiosis infection and growth performance of broilers in experimental trials: insights from a meta-analysis including modulating factors

An infection by protozoa Eimeria spp. can cause coccidiosis, which negatively affects broiler chicken performance and causes economic and production losses. To understand the effect of coccidiosis on broilers' performance, we evaluated the independent variables and their interactions on the severity of coccidiosis in broilers that cause variation (Δ) of average daily feed intake (ADFI), average daily gain (ADG), and gain per feed (G:F) of broiler chicks using a meta-analysis approach. A database of 55 papers describing 63 experiments was gathered; broilers were challenged by Eimeria species (E. acervulina, E. maxima, E. tenella, and mixed) and at least 2 variables among ADFI, ADG, and feed conversion ratio (FCR) were studied. The variation induced by the challenge was calculated relative to the control group of each experiment. The indirect factors evaluated were days postinfection (DPI), Eimeria type and dose, infection age (IA), bird's mean age in the analyzed period, genetic line, sex, and whether they were raised in a cage or a pen. Graphical, correlation, and variance analyses were performed to evaluate the form of the responses. Then, a linear plateau model was adjusted for each response variable as a function of DPI to determine the consequences of the disease on the variation of performance over time after infection. The impact of the infection challenge on the variation of performance vs. nonchallenge broilers was only impacted by DPI (P < 0.05). The adjustment of the data with the linear plateau model allows us to determine the host response to the coccidiosis disease at different stages. At 5 DPI (acute phase), ΔADFI, ΔADG, ΔG:F were of -19.0; -39.8, and -25.5, respectively. After almost 13 DPI birds achieved the recovery phase for all variables with Δ varying from -19 to -3.75% for ADFI, from -39.8 to -10.5% for ADG, and from -25.5 to -7.24% for G:F. The Eimeria impact was higher in ADG than ADFI in all periods due to Eimeria aggressive action form causing lesions in gut epithelial reducing the use of nutrients and energy. The results can be used as a quantitative approach to determine the consequences of Eimeria spp. on broiler performance.

Responses of broilers challenged by Eimeria maxima fed with different levels of dietary balanced protein

This study aimed to evaluate the effects of different dietary balanced protein (BP) levels on the gut health, amino acid apparent ileal digestibility (AID), footpad dermatitis lesions, and litter quality in broiler chicks infected with Eimeria maxima. A total of 2400 male 14-day-old Cobb500 broilers were randomly allotted into 10 treatments with six replications containing 40 birds each in a factorial design of 5 × 2. The treatments consisted of five levels of BP (6.66%, 13.32%, 19.98%, 26.64%, and 33.3%), and broilers unchallenged (NCH) or challenged (CH). Broilers in the CH group received 1 mL of Eimeria maxima inoculum (7 × 103 sporulated oocysts/mL). Oocyst count in excreta, visual intestinal modifications score, morphology, and morphometrics of the ileum were used to determine gut health status. Additionally, amino acids and CP AID, litter quality, and footpad dermatitis were evaluated. An ANOVA and Kruskal-Wallis tests followed by post-hoc tests were performed. The oocyst count in the CH group increased with an increase in dieatary BP (P = 0.08). The incidence of intestinal modifications was higher in the CH group (P < 0.05) and increased with increasing dietary BP (P < 0.05). Morphometrics were impaired by the challenge (P < 0.05), and by the two highest BP levels (P < 0.05). Amino acids AID (methionine, methionine + cystine, arginine, and serine) were reduced by E. maxima challenge. An increase in dietary BP resulted in poor litter quality and high prevalence of of footpad dermatitis (P < 0.05). The E. maxima challenge and increased BP decreased gut health, litter quality, and cause a high incidence of footpad dermatitis.

Applications of Enteroendocrine Cells (EECs) Hormone: Applicability on Feed Intake and Nutrient Absorption in Chickens

This review focuses on the role of hormones derived from enteroendocrine cells (EECs) on appetite and nutrient absorption in chickens. In response to nutrient intake, EECs release hormones that act on many organs and body systems, including the brain, gallbladder, and pancreas. Gut hormones released from EECs play a critical role in the regulation of feed intake and the absorption of nutrients such as glucose, protein, and fat following feed ingestion. We could hypothesize that EECs are essential for the regulation of appetite and nutrient absorption because the malfunction of EECs causes severe diarrhea and digestion problems. The importance of EEC hormones has been recognized, and many studies have been carried out to elucidate their mechanisms for many years in other species. However, there is a lack of research on the regulation of appetite and nutrient absorption by EEC hormones in chickens. This review suggests the potential significance of EEC hormones on growth and health in chickens under stress conditions induced by diseases and high temperature, etc., by providing in-depth knowledge of EEC hormones and mechanisms on how these hormones regulate appetite and nutrient absorption in other species.

Nutritional interventions to support broiler chickens during Eimeria infection

Different combinations of gut health-promoting dietary interventions were tested to support broilers during different stages of Eimeria infection. One-day-old male Ross 308 broilers (n = 720) were randomly assigned to one of 6 dietary treatments, with 6 pens per treatment and 20 birds per pen, for 35 d. At 7 d of age (d7), all birds were inoculated with 1000, 100, and 500 sporulated oocysts of E. acervulina, E. maxima, and E. tenella, respectively. A 4-phase feeding schedule was provided. The dietary treatments (TRT) 1 to 4 included the basal diet supplemented with multispecies probiotics from d0 to 9 and coated butyrate and threonine from d28 to 35 but received four different combinations of prebiotics and phytochemicals from d9 to 18 and d18 to 28. The basal diet for the positive control (PC, TRT5) included diclazuril as a anticoccidial. The negative control (NC, TRT6) contained no anticoccidial. Performance was assessed for each feeding phase, and oocyst output, Eimeria lesion scores, cecal weight, litter quality, and footpad lesions were assessed at d14, d22, d28, and d35. Body weight gain (BWG) and feed intake (FI) were not affected by dietary treatment. PC broilers had the best feed conversion ratio (FCR) of all treatments from d0 to 35 (P < 0.001). None of the dietary treatments resulted in better litter quality or reduced footpad lesions compared to the PC. Moreover, the PC was most effective in reducing oocyst output and lesion scores compared to all other treatments. However, broilers that received the multispecies probiotics (d0 to 9), saponins (d9 to 18), saponins, artemisin, and curcumin (d18 to 28), and coated butyrate and threonine (d28 to 35) had the best FCR (P < 0.001) and lowest oocyst output and lesion scores compared to other dietary treatments. This study suggests that although the tested compounds did not perform as well as the anticoccidial, when applied in the proper feeding period, they may support bird resilience during coccidiosis infection.

Quantifying the effect of coccidiosis on broiler performance and infection outcomes in the presence and absence of control methods

A systematic review and meta-analysis was conducted to investigate the role of Eimeria species, dose and inoculation time, on performance and infection outcomes of different broiler strains infected for different study durations. The meta-analysis addressed E. acervulina, E. maxima, E. tenella, and mixed species infections, and involved data from 72 peer-reviewed articles, corresponding to 521 treatments performed on 20,756 broilers. A secondary objective was to investigate the effects of synthetic anticoccidials, ionophores, and vaccination against Eimeria on the above outcomes. Performance during infection was scaled (%) to that of the uninfected birds. Infection reduced scaled ADFI and ADG (P < 0.001) and increased feed conversion ratio (FCR; P < 0.05); there was a significant interaction between dose and species on scaled ADFI and ADG, suggesting that different species affected these variables to different extents (P < 0.001). There was a tendency for an interaction between dose and broiler strain on scaled ADFI (P = 0.079), and a significant interaction between these variables on scaled ADG (P < 0.01). A tendency for an interaction between oocyst dose and Eimeria species (P = 0.067) on maximum number of oocysts excreted was observed. Lesion scores were significantly affected by dose, species, and their interaction (P < 0.05), the latter caused by an increase in the lesion scores during E. maxima and E. tenella infections. Control methods significantly affected scaled ADG and FCR (P < 0.05) and there was an interaction between dose and control methods on ADFI (P < 0.001). Synthetic anticoccidial use improved scaled ADG (P < 0.01), whereas ionophores improved FCR compared with untreated birds (P < 0.01). An interaction between dose and control method on scaled ADFI was caused by the higher ADFI of vaccinated compared to untreated birds, as dose increased. There was a significant effect of control methods on lesion scores (P < 0.01). All findings advance our understanding of the factors that influence the impact of coccidiosis and its controls in broilers.

Starving for nutrients: anorexia during infection with parasites in broilers is affected by diet composition

In 2 experiments, we investigated whether diet composition plays a role in pathogen-induced anorexia, the voluntary reduction in ADFI during infection in broilers. We hypothesized that either energy or CP dietary content could influence the extent of anorexia in Ross 308 broilers and infection outcomes with Eimeria maxima. From d 13 of age, half of the birds were infected, and half were uninfected. ADFI was measured daily, and BW every 3 d until d 29. Oocyst excretion was measured daily from d 17 to 23. The impact of parasitism on the small intestine was assessed on d 19 and 25. In Experiment 1, 336 birds were offered diets progressively diluted with lignocellulose, starting from a diet with 3,105 (kcal ME/kg) and 20% CP. There was a significant interaction between infection and diet on ADFI during the acute stage of infection (d 17 to 21): for control birds diet dilution decreased ADFI and consequently reduced energy and CP intake. For infected birds, diet dilution increased ADFI, leading to the same energy and CP intake across diets. Oocyst excretion and villi length to crypt depth ratio (VCR) were constant across infected treatments. In Experiment 2, 432 birds were offered diets with constant ME (3,105 kcal/kg), but different CP contents (24, 20, 26, and 12%). Infection significantly reduced ADFI. Although there was no interaction between infection and diet on ADFI, there was an interaction on CP intake during the acute stage of infection. Infected birds on the 20% CP diet achieved the same CP intake as uninfected birds. There were no differences in the VCR and ADG of the infected birds on 24, 20 and 16% CP treatments, but birds on 12% had the lowest ADG and excreted more oocysts. We suggest that during infection, birds target a nutrient resource intake, which appears to be beneficial for infection outcomes, while at the same time they avoid excess protein intake. We conclude that different mechanisms regulate ADFI in infected and uninfected birds.

Centennial Review: Factors affecting the chicken gastrointestinal microbial composition and their association with gut health and productive performance

Maintenance of "gut health" is considered a priority in commercial chicken farms, although a precise definition of what constitutes gut health and how to evaluate it is still lacking. In research settings, monitoring of gut microbiota has gained great attention as shifts in microbial community composition have been associated with gut health and productive performance. However, microbial signatures associated with productivity remain elusive because of the high variability of the microbiota of individual birds resulting in multiple and sometimes contradictory profiles associated with poor or high performance. The high costs associated with the testing and the need for the terminal sampling of a large number of birds for the collection of gut contents also make this tool of limited use in commercial settings. This review highlights the existing literature on the chicken digestive system and associated microbiota; factors affecting the gut microbiota and emergence of the major chicken enteric diseases coccidiosis and necrotic enteritis; methods to evaluate gut health and their association with performance; main issues in investigating chicken microbial populations; and the relationship of microbial profiles and production outcomes. Emphasis is given to emerging noninvasive and easy-to-collect sampling methods that could be used to monitor gut health and microbiological changes in commercial flocks.

Evaluating endogenous loss and standard ileal digestibility of amino acids in response to the graded severity levels of E. maxima infection

The study was conducted to evaluate the effects of graded levels of Eimeria maxima challenge on endogenous loss, apparent ileal digestibility (AID), and standard ileal digestibility (SID) of amino acids. A total of 768 fourteen-day-old male Cobb 500 broiler chickens were randomly allocated into 64 battery cages. Apart from the regular corn-soybean based diet, the nitrogen-free diet (NFD) was formulated to determine the endogenous loss of amino acids. One-half of the birds (32 cages) were fed the NFD, and another half fed the regular diet from d 14 to 20. Both groups were further assigned to 4 treatments (nonchallenged control or three levels of challenge doses) with 8 replicate cages. The challenge doses were: the low challenge dose (Low) with E. maxima 12,500 oocysts, the medium challenge dose (Medium) with 25,000 E. maxima oocysts, and the high challenge dose (High) with 50,000 E. maxima oocysts. At 6 d postinfection, ileal digesta samples were collected and the intestinal lesion score were recorded. The results indicated a significant linear increase of endogenous amino acid flow in response to the graded E. maxima challenge. Moreover, the AID and SID of amino acids were linearly reduced due to the increasing challenge dose. The study demonstrated that NFD significantly reduced lesion scores, underestimating the true endogenous losses of birds fed regular diets. Even though the endogenous loss of amino acids was underestimated, they were linearly increased in response to the graded E. maxima challenge. In conclusion, the higher Eimeria dose birds were challenged with, the more endogenous amino acids were released into the intestine and the lower dietary nutrients were digested and absorbed by broiler chickens.

Exogenous Enzymes Influenced Eimeria-Induced Changes in Cecal Fermentation Profile and Gene Expression of Nutrient Transporters in Broiler Chickens

Two 21-day experiments were conducted to investigate the effects of exogenous enzymes on growth performance, tight junctions, and nutrient transporters, jejunal oligosaccharides and cecal short-chain fatty acids (SCFA) of broiler chickens challenged with mixed Eimeria. Two different basal diets: high fiber-adequate protein (HFAP; Expt. 1) or low fiber-low protein (LFLP; Expt. 2) were used in the two experiments. In each experiment, birds were allocated to four treatments in a 2 × 2 factorial arrangement (with or without protease and xylanase combination; with or without Eimeria challenge). In Expt. 1, with HFAP diets, Eimeria upregulated (p < 0.05) the expression of claudin-1, but downregulated (p < 0.05) glucose transporters GLUT2/GLUT5. On the contrary, enzymes downregulated (p < 0.05) claudin-1 and alleviated the Eimeria-depressed GLUT2/GLUT5 expression. In both experiments, Eimeria decreased (p < 0.05) cecal saccharolytic SCFA and increased (p < 0.05) cecal branched-chain fatty acids. The challenge × enzyme interaction (p < 0.05) showed that enzymes reversed the Eimeria effects on fermentation pattern shift. In conclusion, Eimeria altered tight junctions and nutrient transporters expression promoted cecal proteolytic fermentation and inhibited saccharolytic fermentation. Exogenous enzymes showed the potential of alleviating the Eimeria-induced intestinal gene expression changes and reversing the unfavorable cecal fermentation pattern.

Impacts of increasing challenge with Eimeria maxima on the growth performance and gene expression of biomarkers associated with intestinal integrity and nutrient transporters

This study was conducted to investigate the impacts of graded severity of Eimeria maxima infection on the growth performance and intestine health of broiler chickens. Four different levels of E. maxima-challenged treatments were used, including a non-challenged control group, a low challenge (12 500 oocysts), a medium challenge (25 000 oocysts), and a high challenge dose (50 000 oocysts). There were eight replicate cages per treatment, with 12 birds in each cage, and chickens in the challenged groups orally received sporulated oocysts on day 14. Gastrointestinal permeability was measured by fluorescein isothiocyanate dextran at 5 days post-infection (dpi), whereas intestinal morphology and gene expression of nutrient transporters and tight junction proteins were determined at 6 dpi. The results demonstrate a linear reduction in growth performance, jejunal villus height, and jejunal integrity with graded challenge doses of E. maxima (P < 0.01). Moreover, linear regulation of nutrient transporters and tight junction proteins was a consequence of increasing Eimeria infection levels (P < 0.01). The linear increase of Claudin 1, cationic amino acid transporter, glucose transporter 1, and L-type amino acid transporter genes was associated with increased severity of coccidiosis (P < 0.01). Furthermore, expression of nutrient transporters located at the brush border membrane were down-regulated (P < 0.01) with increasing E. maxima inoculation dose. In conclusion, growth performance and key intestinal integrity biomarkers in broiler chickens were adversely influenced in a dose-dependent manner by E. maxima infection.

Network meta-analysis comparing the effectiveness of anticoccidial drugs and anticoccidial vaccination in broiler chickens

With the trend to organic production and concerns about using antibiotic feed additives, the control of infections with Eimeria spp. in broiler flocks has become more difficult. Vaccination against coccidia is an alternative, but there are concerns that the live vaccines used might have negative effects on production parameters and intestinal health. Reports of experiments directly comparing anticoccidial drugs and anticoccidial vaccines are rare. This network meta-analysis (NMA) identified and analyzed 61 articles reporting 63 experiments testing anticoccidial drugs and anticoccidial vaccines under conditions resembling commercial broiler production. The effect sizes were mean differences in body weight/body weight gain (BW/BWG) and feed conversion rate (FCR) between the 175 included groups. The results show that groups vaccinated against coccidia have a similar BW/BWG and FCR at processing age compared to groups given anticoccidial drugs. However, the results tended to be more favorable for anticoccidial drugs than for vaccines. The analysis of eight subsets, containing only groups (1) groups that had not received an AGP in addition to an anticoccidial drug, (2) groups that had not received ionophores, (3) groups that had not received chemicals, (4) groups that had not received an attenuated vaccine, (5) groups that had not received a fully virulent vaccine, (6) groups that were not additionally challenged with bacteria or not challenged, (7) groups that had received a severe challenge as defined by a total infection dose of more than 100,000 oocysts or were not challenged, (8) groups that were challenged on day 15 or earlier or not challenged brought similar results and confirmed the robustness of the NMA. In addition, the analysis exposes unnecessary, as well as inherent, problems with data quality, which every researcher working with coccidia should carefully consider, and identifies under-researched areas that should be addressed in future research.

Molecular detection of Eimeria species and Clostridium perfringens in poultry dust and pooled excreta of commercial broiler chicken flocks differing in productive performance

Necrotic enteritis and coccidiosis are the most economically detrimental enteric diseases of broiler chickens. This study aimed to investigate the association of DNA load of Clostridium perfringens, netB, and five Eimeria species (E. brunetti, E. maxima, E. necatrix, E. acervulina and E. tenella) in poultry house dust and pooled excreta with flock productive performance. The dust and pooled excreta from the floor were collected weekly at days 7, 14, 21, 28 and 35 of chicken age from 16 flocks of eight farms from two Australian integrator companies. The farms were ranked as high or low performers by each integrator according to the production performance of studied flocks. Eimeria tenella and necatrix were not detected in any farm while E. brunetti was detected in a low-performance farm and netB was detected in a high-performance farm. C. perfringens, E. acervulina and E. maxima DNA were detected on all farms with no significant differences in DNA load between high and low-performance farms or companies. The lack of association of pathogen DNA load and farm performance is possibly due to overall low to moderate pathogen DNA load detected in this study. Further studies on a larger number of farms are needed to determine whether these population level measurements of key pathogens based on PCR detection of nucleic acids are correlated with performance variables.

Secondary Functions of Arginine and Sulfur Amino Acids in Poultry Health: Review

Simple Summary

Historically, studies with amino acids have focused on protein synthesis and accretion, especially with eggs and meat, whereas less importance has been given to their secondary functions on the metabolism. However, certain amino acids, such as arginine, methionine, and cysteine are precursors for other essential molecules in the immune defense, antioxidant system, cell signaling, and gene expression, and can act as regulators in the growth and development of the animals. Because poultry are subjected to stressful conditions throughout their lives, the use of these amino acids and their secondary functions could beneficiate their general health. This review describes the metabolism of arginine, methionine, and cysteine and how they modulate different tissues, especially during challenging conditions. Arginine supplementation has been shown to modulate musculoskeletal health development, reduce fat accretion, and improve the antioxidant system. Moreover, methionine and cysteine could improve the bone development and have a potential in mitigating the negative effects caused by heat stress. Understanding how these amino acids can ameliorate stressful conditions may provide novel insights about their use as nutritional strategies to modulate the health status of chickens.

Abstract

Amino acids such as arginine, methionine, and cysteine are the precursors of essential molecules that regulate growth and health, being classified as functional amino acids. This review describes the metabolism of arginine and the sulfur amino acids and how they modulate, directly or indirectly, different tissues. Emphasis is placed on their effects in supporting health during challenging conditions, such as heat stress and Eimeria infection. The use of arginine has been shown to reduce abdominal fat pad in ducks and increase lean tissue and bone mineral density in broilers. Additionally, the sulfur amino acids have been shown to improve bone development and are beneficial during heat stress. The use of L-methionine increased the cortical and trabecular bone mineral densities, in laying hens. Moreover, the dietary inclusion of these amino acids could reduce the damage caused by Eimeria spp. infection by regulating the antioxidant system and cell repair. Understanding how these amino acids can mitigate stressful conditions may provide us novel insights of their use as nutritional strategies to modulate the health status of chickens.

Revisiting the Economic Impacts of Eimeria and Its Control in European Intensive Broiler Systems With a Recursive Modeling Approach

Ionophore compounds active against Eimeria species are widely used in intensive broiler systems and have formed the backbone of coccidiosis control for almost 50 years. Producers, however, are under pressure to reduce ionophore use due to consumer concerns over antimicrobial usage in food animals, and antimicrobial resistance. Moreover, current vaccines against Eimeria are commonly considered to be less cost-effective in intensive broiler systems, especially in Europe where attenuated live vaccines are used. An economic assessment of the impact of Eimeria and the disease coccidiosis, including the cost implications of different efficacies of control, is therefore timely to provide evidence for industry and policy development. A mechanistic model of broiler production under varying infection and control states was used to construct a dataset from which system productivity can be measured. Coccidiosis impact increased rapidly as control efficacy decreased. In the total absence of control, median impact was found to maximize at between €2.55 and €2.97 in lost production per meter squared of broiler house over a 33 day growing period. Coccidiosis remains a major risk to intensive broiler systems and the model developed allows investigation of issues related to coccidiosis control, antimicrobial use and the development of antimicrobial resistance.

The effects of total sulfur amino acids on the intestinal health status of broilers challenged with Eimeria spp

This study evaluated the effects of total sulfur amino acid (TSAA) levels on the performance and intestinal health of broilers challenged with Eimeria spp. A total of 432 one-day-old off-sex Cobb 500 male chicks were randomly assigned to a 3 × 2 factorial arrangement (6 replicates/12 birds), with diets and Eimeria challenge as the main factors. The diets were as follows: 70% (no methionine [Met] supplementation), 85, and 100% TSAA, supplemented with L-Met. At day 14, the challenged birds (n = 216) were orally gavaged with a pool of Eimeria acervulina, Eimeria maxima, and Eimeria tenella sporulated oocysts, and the unchallenged birds (n = 216) received water. At 6 and 12 D post inoculation (dpi), performance and intestinal health were evaluated. The challenge, regardless of diets, significantly impaired the performance, intestinal villi height, villus-to-crypt ratio, and ileal digestibility of dry matter, energy, and crude protein (CP) and modulated the tight junction protein (TJP) expression throughout the experiment. Moreover, the superoxide dismutase activity was increased, whereas the reduced glutathione (GSH)-to-oxidized glutathione (GSSG) ratio was decreased by the challenge at 6 dpi. Regardless of the challenge, the 70% TSAA diet reduced the body weight and feed intake in all phases, whereas the ileal digestibility of CP was higher in birds fed with the 70% TSAA diet than in those fed with the 100% TSAA diet at 6 dpi. No major differences were observed among the diets with regard to the intestinal histomorphology and TJP expression, and birds fed with the 100% TSAA diet had the highest GSH concentration at 12 dpi. Few interactions were observed, and the Met supplementation counteracted the negative effects of the Eimeria challenge on GSH concentration when 85 and 100% of TSAA levels were reached. Overall, the Eimeria challenge had a negative impact on growth and intestinal health. Moreover, the supplementation of L-Met until either 85 or 100% of TSAA levels were reached was enough to assure good performance and intestinal health in birds challenged or not challenged with Eimeria spp.

Dietary supplementation with anti-IL-10 antibody during a severe Eimeria challenge in broiler chickens

Attenuation of host IL-10 activity during Eimeria infection may elicit a robust Th1 response to eliminate the parasite from the gut epithelium. An experiment was conducted to study the effects of feeding IL-10 neutralizing antibody delivered via a dried egg product (DEP) on growth performance, immune responsivity, and gut health outcomes during a severe challenge with either Eimeria acervulina (study 1) or Eimeria tenella (study 2) following FDA CVM #217 protocol to test anticoccidial products. A total of 720 male Ross 308 chicks were used in each study, with 15 replicate cages of 12 birds and the following 4 treatments: sham-inoculated (uninfected) control diet (UCON), Eimeria-infected control diet (ICON), and Eimeria-infected control diet supplemented with DEP at 2 levels (165 [I-165] or 287 [I-287] U/tonne in study 1 and 143 [I-143] or 287 [I-287] U/tonne in study 2). Individual birds assigned to infected treatment groups received a single oral dose of either 200,000 E. acervulina (study 1) or 80,000 E. tenella (study 2) oocysts at 12 d of age (i.e., d post inoculation [DPI] 0), whereas uninfected birds were sham-inoculated with tap water. A one-way ANOVA was performed on outcomes including growth performance, hematology, serum chemistry profiles, immunophenotyping profiles, and intestinal lesion scores. In both studies, DPI 0 to 7 weight gain, feed intake, and feed conversion ratio were worse (P < 0.05) in all infected groups compared with the UCON group. Compared with ICON, DEP supplementation elicited no differences on overall growth performance. Histopathology and lesion scores revealed severe damage to the gut epithelium owing to the Eimeria challenge, yet DEP supplementation did not improve these outcomes or oocyst shedding, hematological measurements, or serum chemistry. However, DEP supplementation improved (P < 0.05) the percentage of circulating CD3⁺ cells at 6 DPI in study 2. These results indicate that DEP does not appear to elicit a coccidiostatic effect during a severe infection with E. acervulina or E. tenella.

Graded Eimeria challenge linearly regulated growth performance, dynamic change of gastrointestinal permeability, apparent ileal digestibility, intestinal morphology, and tight junctions of broiler chickens

This study was conducted to evaluate graded Eimeria challenge on growth performance, apparent ileal digestibility, gastrointestinal permeability, intestinal morphology, gene expression of tight junction protein, and intestinal lesion scores in broiler chickens. There were 5 groups in this study, including a control and 4 different Eimeria treatment doses. A mixed Eimeria spp. solution with 50,000 Eimeria maxima, 50,000 Eimeria tenella, and 250,000 Eimeria acervulina per milliliter was prepared for the high-dose challenge treatment. The 2-fold serial dilution was used to make the medium-high (25,000 E. maxima; 25,000 E. tenella; 125,000 E. acervulina), the medium-low (12,500 E. maxima; 12,500 E. tenella; 62,500 E. acervulina), and the low challenge dose (6,250 E. maxima; 6,250 E. tenella; 31,250 E. acervulina). A total of three hundred sixty 13-day-old male broiler chickens were randomly allocated into 5 treatments with 6 replicated cages. Growth performance was calculated from 0 to 6 D postinfection (DPI). Intestine lesion was scored on 6 DPI. Gastrointestinal permeability was measured on 3, 5, 6, 7, and 9 DPI. The results indicated significant linear reduction in growth performance, intestinal villi height, and ileal nutrient digestibility in response to the increase of Eimeria challenge dose. Furthermore, gene expression of tight junction protein was linearly upregulated by the increasing challenge doses. Significant linear increases of gastrointestinal permeability were found on 5, 6, and 7 DPI (P < 0.01). On 9 DPI, the gastrointestinal permeability was recovered back to normal level in the challenge groups. In conclusion, the higher Eimeria doses birds received, the more severe intestine damage was observed in several gastrointestinal health parameters. The medium-low or medium-high levels of mixed Eimeria oocysts is suggested as an optimum Eimeria-challenge dose to establish a subclinical challenge model for future studies evaluating nutritional strategies. Moreover, it is recommended to measure gastrointestinal permeability on 5 DPI with higher oocysts doses and 6 DPI when using the lower oocysts doses.

Dietary vitamin D improves performance and bone mineralisation, but increases parasite replication and compromises gut health in Eimeria-infected broilers

Coccidial infections reduce fat-soluble vitamin status and bone mineralisation in broiler chickens. We hypothesised that broilers infected with Eimeria maxima would benefit from increased dietary supplementation with vitamin D (vitD) or with 25-hydroxycholecalciferol (25(OH)D3 or 25D3). Broilers were assigned to diets with low (L) or commercial (M) vitD levels (25 v. 100 μg/kg) supplemented as cholecalciferol (D3) or 25D3. At day 11 of age, birds were inoculated with water or 7000 E. maxima oocysts. Pen performance was calculated over the early (days 1-6), acute (days 7-10) and recovery periods (days 11-14) post-infection (pi). At the end of each period, six birds per treatment were dissected to assess long bone mineralisation, plasma levels of 25D3, Ca and P, and intestinal histomorphometry. Parasite replication and transcription of cytokines IL-10 and interferon-γ (IFN-γ) were assessed at day 6 pi using quantitative PCR. Performance, bone mineralisation and plasma 25D3 levels were significantly reduced during infection (P < 0·05). M diets or diets with 25D3 raised plasma 25D3, improved performance and mineralisation (P < 0·05). Offering L diets compromised feed efficiency pi, reduced femur breaking strength and plasma P levels at day 10 pi in infected birds (P < 0·05). Contrastingly, offering M diets or diets with 25D3 resulted in higher parasite loads (P < 0·001) and reduced jejunal villi length at day 10 pi (P < 0·01), with no effect on IL-10 or IFN-γ transcription. Diets with M levels or 25D3 improved performance and mineralisation, irrespective of infection, while M levels further improved feed efficiency and mineralisation in the presence of coccidiosis.

Does selection for growth rate in broilers affect their resistance and tolerance to Eimeria maxima?

Chickens exhibit varied responses to infection with Eimeria parasites. We hypothesise that broilers selected for increased growth rate will show lower resistance and tolerance to a coccidian challenge. 288 chickens of fast (F) or slow (S) growing lines were inoculated with 0 (control), 2500 (low-dose), or 7000 (high-dose) sporulated E. maxima oocysts at 13 days of age in two consecutive rounds. Gain and Intake were measured daily and their values relative to BW at the point of infection were calculated over the pre-patent (days 1-4 post-infection), acute (d5-8 pi), and recovery (d9-12 pi) phases of infection to assess the impact of infection. Levels of plasma carotenoids, vitamins E and A, long bone mineralisation, caecal microbiota diversity indices, and histological measurements were assessed at the acute (d6 pi) and recovery stage (d13 pi). In addition, we measured the levels of nitric oxide metabolites and the number of parasite genome copies in the jejunumat d6pi. In absolute terms F birds grew 1.42 times faster than S birds when not infected. Infection significantly reduced relative daily gain and intake (P < 0.001), with the effects being most pronounced during the acute phase (P < 0.001). Levels of all metabolites were significantly decreased, apart from NO which increased (P < 0.001) in response to infection on d6pi, and were accompanied by changes in histomorphometric features and the presence of E. maxima genome copies in infected birds, which persisted to d13pi. Furthermore, infection reduced tibia and femur mineralisation, which also persisted to d13pi. Reductions in measured variables were mostly independent of dose size, as was the level of parasite replication. The impact of infection was similar for S and F-line birds for all measured parameters, and there were no significant interactions between line x dose size on any of these parameters. In conclusion, our results suggest that line differences in productive performance do not influence host responses to coccidiosis when offered nutrient adequate diets.

Expression of host defense peptides in the intestine of Eimeria-challenged chickens

Avian coccidiosis is caused by the intracellular protozoan Eimeria, which produces intestinal lesions leading to weight gain depression. Current control methods include vaccination and anticoccidial drugs. An alternative approach involves modulating the immune system. The objective of this study was to profile the expression of host defense peptides such as avian beta-defensins (AvBDs) and liver expressed antimicrobial peptide 2 (LEAP2), which are part of the innate immune system. The mRNA expression of AvBD family members 1, 6, 8, 10, 11, 12, and 13 and LEAP2 was examined in chickens challenged with either E. acervulina, E. maxima, or E. tenella. The duodenum, jejunum, ileum, and ceca were collected 7 d post challenge. In study 1, E. acervulina challenge resulted in down-regulation of AvBD1, AvBD6, AvBD10, AvBD11, AvBD12, and AvBD13 in the duodenum. E. maxima challenge caused down-regulation of AvBD6, AvBD10, and AvBD11 in the duodenum, down-regulation of AvBD10 in the jejunum, but up-regulation of AvBD8 and AvBD13 in the ceca. E. tenella challenge showed no change in AvBD expression in any tissue. In study 2, which involved challenge with only E. maxima, there was down-regulation of AvBD1 in the ileum, AvBD11 in the jejunum and ileum, and LEAP2 in all 3 segments of the small intestine. The expression of LEAP2 was further examined by in situ hybridization in the jejunum of chickens from study 2. LEAP2 mRNA was expressed similarly in the enterocytes lining the villi, but not in the crypts of control and Eimeria challenged chickens. The lengths of the villi in the Eimeria challenged chickens were less than those in the control chickens, which may in part account for the observed down-regulation of LEAP2 mRNA quantified by PCR. Overall, the AvBD response to Eimeria challenge was not consistent; whereas LEAP2 was consistently down-regulated, which suggests that LEAP2 plays an important role in modulating an Eimeria infection.

Establishment of an in vitro chicken epithelial cell line model to investigate Eimeria tenella gamete development

Background

Eimeria tenella infection leads to acute intestinal disorders responsible for important economic losses in poultry farming worldwide. The life-cycle of E. tenella is monoxenous with the chicken as the exclusive host; infection occurs in caecal epithelial cells. However, in vitro, the complete life-cycle of the parasite has only been propagated successfully in primary chicken kidney cells, which comprise undefined mixed cell populations; no cell line model has been able to consistently support the development of the sexual stages of the parasite. We therefore sought to develop a new model to study E. tenella gametogony in vitro using a recently characterised chicken cell line (CLEC-213) exhibiting an epithelial cell phenotype.

Methods

CLEC-213 were infected with sporozoites from a precocious strain or with second generation merozoites (merozoites II) from wild type strains. Sexual stages of the parasite were determined both at the gene and protein levels.

Results

To our knowledge, we show for the first time in CLEC-213, that sporozoites from a precocious strain of E. tenella were able to develop to gametes, as verified by measuring gene expression and by using antibodies to a microgamete-specific protein (EtFOA1: flagellar outer arm protein 1) and a macrogamete-specific protein (EtGAM-56), but oocysts were not observed. However, both gametes and oocysts were observed when cells were infected with merozoites II from wild type strains, demonstrating that completion of the final steps of the parasite cycle is possible in CLEC-213 cells.

Conclusion

The epithelial cell line CLEC-213 constitutes a useful avian tool for studying Eimeria epithelial cell interactions and the effect of drugs on E. tenella invasion, merogony and gametogony.

Mitochondrial pathways are involved in Eimeria tenella-induced apoptosis of chick embryo cecal epithelial cells

Accumulating evidence suggests that Eimeria tenella severely damages the intestinal mucosa in infected poultry, resulting in deadly haemorrhagic typhlocolitis and major economic losses. Damage to host tissue is believed to arise mainly from apoptosis, which is, in general, intimately related to mitochondrial function. However, it is unclear whether mitochondria-dependent apoptotic pathways are specifically involved in parasite-induced apoptosis of chick embryo cecal epithelial cells. Because the mitochondrial permeability transition pore (MPTP) and caspase-9 are important elements in these pathways, we studied the effects of their respective inhibitors (i.e., cyclosporine A [CsA] and Z-LEHD-FMK, respectively) in primary cultures of chicken embryonic cecum epithelial cells using histopathological techniques, terminal deoxynucleotidyl transferase-mediated dUTP nick end labelling (TUNEL) assays, flow cytometry (FCM) and ELISA. Results indicated that the inhibitors significantly decreased (p < 0.01) DNA injury, apoptosis and caspase-9 and caspase-3 activity of chick embryo cecal epithelial cells at 24, 48, 72, 96 and 120 h after E. tenella infection. Thus, our data supported that mitochondria-dependent apoptotic pathways were involved in apoptosis of parasitised chick embryo cecal epithelial cells.

The effect of the mitochondrial permeability transition pore on apoptosis in Eimeria tenella host cells

Although the mitochondrial permeability transition pore (MPTP) is associated with cellular apoptosis and necrosis, its effect in host response to Eimeria infections is not well understood. In an effort to better understand the effect of MPTP on apoptosis in Eimeria tenella host cells, an MPTP inhibitor (cyclosporin A) was used to inhibit MPTP opening in vitro. Cecal epithelial cells from chick embryos, which were either treated or non-treated with cyclosporin A, were used as Eimeria tenella host cells. In addition, primary chick embryo cecum epithelial cell culture techniques and flow cytometry were used to detect the dynamic changes in MPTP opening, mitochondrial transmembrane potential, and cell apoptosis rate of Eimeria tenella host cells. Compared with the control group, cytometric techniques showed that untreated host cells exhibited a significantly higher (P < 0.01) degree of MPTP opening but lower (P < 0.01 or P < 0.05) mitochondrial transmembrane potential. Moreover, untreated group cells had less apoptosis (P < 0.01) at 4 h and more apoptosis (P < 0.05 or P < 0.01) at 24 to 120 h as compared with control group cells. After the application of cyclosporin A, the degree of MPTP opening in the treated group was significantly lower (P < 0.01) at 4 to 120 h compared to the untreated group, whereas the treated group had higher (P < 0.05 or P < 0.01) mitochondrial transmembrane potentials at 24 to 120 h. Flow cytometry assays also showed that there was less (P < 0.05 or P < 0.01) apoptosis after 24 h in the treated group than in the untreated group. Taken together, these observations indicate that MPTP is a key node that plays a predominant role in the mitochondrial apoptosis pathway in the host cell induced by Eimeria tenella.

Investigation of the effect of coccidial vaccine challenge on apparent and standardized ileal amino acid digestibility in grower and finisher broilers and its evaluation in 21-day-old broilers

The effect of coccidial vaccine challenge (CVC, Coccivac(®)B; challenged, CHA; or unchallenged, NCH) on ileal endogenous amino acid (IEAA) losses and standardized ileal AA digestibility (SIAAD) in 21- and 42-day-old broilers fed a corn-soybean meal-dried distillers' grains with solubles-poultry by-product meal-based diet (Expt. 1) and the effect of supplemental AA in ameliorating the effect of CVC (Expt. 2) were evaluated. Expt. 1 was designed as a 2 (d 21 or 42) x 2 (NCH or CHA) factorial arrangement of treatments with 8 replicates in a complete randomized design. The CVC birds were gavaged with 12 x coccidial vaccine on d 15 and 36 and were sampled on 6 d post challenge. SIAAD was determined by correcting apparent ileal AA digestibility for IEAA losses. Feed intake (FI) and BW gain were higher (P ≤ 0.05) in 21-day-old NCH birds compared to the 21-day-old CHA birds while 42-day-old birds had higher FI and BW gain than 21-day-old NCH and CHA birds. Ileal endogenous nitrogen loss was higher (P ≤ 0.05) in 42-day-old CHA birds compared to 42-day-old NCH birds. Apparent ileal AA digestibility in 21-day-old CHA birds was lower (P ≤ 0.05) than for 21-day-old NCH and 42-day-old NCH and CHA birds. SIAAD in 21-day-old CHA birds was lower (indispensable AA = 15.2 and dispensable AA = 17.8%-unit; P ≤ 0.05) than for 21-day-old NCH and 42-day-old NCH and CHA birds. Apparent ileal digestibility and total tract utilization of DM, N, and energy were not different between d 21 NCH and d 42 NCH and CHA birds but higher (P ≤ 0.05) than for d 21 CHA birds. Supplemental AA restored feed efficiency, but not BW gain, to that of the positive control (0.715 vs. 0.737). Results from Expt.1 showed that CVC significantly influenced ileal AA digestibility in 21- but not in 42-day-old birds. Expt. 2 showed that consideration of SIAAD in feed formulation may benefit feed efficiency.

Large-scale investigation of the parameters in response to Eimeria maxima challenge in broilers

Coccidiosis, a parasitic disease of the intestinal tract caused by members of the genera Eimeria and Isospora, is one of the most common and costly diseases in chicken. The aims of this study were to assess the effect of the challenge and level of variability of measured parameters in chickens during the challenge with Eimeria maxima. Furthermore, this study aimed to investigate which parameters are the most relevant indicators of the health status. Finally, the study also aimed to estimate accuracy of prediction for traits that cannot be measured on large scale (such as intestinal lesion score and fecal oocyst count) using parameters that can easily be measured on all animals. The study was performed in 2 parts: a pilot challenge on 240 animals followed by a large-scale challenge on 2,024 animals. In both experiments, animals were challenged with 50,000 Eimeria maxima oocysts at 16 d of age. In the pilot challenge, all animals were measured for BW gain, plasma coloration, hematocrit, and rectal temperature and, in addition, a subset of 48 animals was measured for oocyst count and the intestinal lesion score. All animals from the second challenge were measured for BW gain, plasma coloration, and hematocrit whereas a subset of 184 animals was measured for intestinal lesion score, fecal oocyst count, blood parameters, and plasma protein content and composition. Most of the parameters measured were significantly affected by the challenge. Lesion scores for duodenum and jejunum (P < 0.001), oocyst count (P < 0.05), plasma coloration for the optical density values between 450 and 490 nm (P < 0.001), albumin (P < 0.001), α1-globulin (P < 0.01), α2-globulin (P < 0.001), α3-globulin (P < 0.01), and β2-globulin (P < 0.001) were the most strongly affected parameters and expressed the greatest levels of variation. Plasma protein profiles proved to be a new, reliable parameter for measuring response to Eimeria maxima. Prediction of intestinal lesion score and fecal oocyst count using the other parameters measured was not very precise (R2 < 0.7). The study was successfully performed in real raising conditions on a large scale. Finally, we observed a high variability in response to the challenge, suggesting that broilers' response to Eimeria maxima has a strong genetic determinism, which may be improved by genetic selection.

Calcium homeostasis in mitochondrion-mediated apoptosis of chick embryo cecal epithelial cells induced by Eimeria tenella infection

In this study, the process of Eimeria tenella-induced apoptosis and the effect of calcium homeostasis were investigated in chick embryo cecal epithelial cells. In particular, we examined cytochrome c release into the cytoplasm, mitochondrial permeability transition pore (MPTP) opening, and changes in [Ca(2+)]c and apoptosis in host cells. Apoptosis, MPTP opening, cytochrome c release, and [Ca(2+)]c in host cells increased following infection. This trend was reversed by blocking the increase in [Ca(2+)]c using BAPTA/AM and EGTA (intra- and extracellular chelators of Ca(2+), respectively) and by applying heparin sodium and ryanodine (blockers of the inositol triphosphate and ryanodine receptors of the endoplasmic reticulum, respectively). These results indicate that [Ca(2+)]c plays a significant role in host cell mitochondrial apoptosis, which is induced via modulation of extracellular Ca(2+) levels and endoplasmic reticulum Ca(2+) channels. Thus, agents that restore Ca(2+) homeostasis may be useful for managing E. tenella infection in chickens.

Reduced parasite motility and micronemal protein secretion by a p38 MAPK inhibitor leads to a severe impairment of cell invasion by the apicomplexan parasite Eimeria tenella

E. tenella infection is associated with a severe intestinal disease leading to high economic losses in poultry industry. Mitogen activated protein kinases (MAPKs) are implicated in early response to infection and are divided in three pathways: p38, extracellular signal-regulated protein kinase (ERK) and c-Jun N-terminal kinase (JNK). Our objective was to determine the importance of these kinases on cell invasion by E. tenella. We evaluated the effect of specific inhibitors (ERK: PD98059, JNKII: SP600125, p38 MAPK: SB203580) on the invasion of epithelial cells. Incubation of SP600125 and SB203580 with epithelial cells and parasites significantly inhibited cell invasion with the highest degree of inhibition (90%) for SB203580. Silencing of the host p38α MAPK expression by siRNA led to only 20% decrease in cell invasion. In addition, when mammalian epithelial cells were pre-treated with SB203580, and washed prior infection, a 30% decrease in cell invasion was observed. This decrease was overcome when a p38 MAPK activator, anisomycin was added during infection. This suggests an active but limited role of the host p38 MAPK in this process. We next determined whether SB203580 has a direct effect on the parasite. Indeed, parasite motility and secretion of micronemal proteins (EtMIC1, 2, 3 and 5) that are involved in cell invasion were both decreased in the presence of the inhibitor. After chasing the inhibitor, parasite motility and secretion of micronemal proteins were restored and subsequently cell invasion. SB203580 inhibits cell invasion by acting partly on the host cell and mainly on the parasite.

Effect of coccidia challenge and natural betaine supplementation on performance, nutrient utilization, and intestinal lesion scores of broiler chickens fed suboptimal level of dietary methionine

The aim of the present experiment was to examine the effect of coccidia challenge and natural betaine supplementation on performance, nutrient utilization, and intestinal lesion scores of broiler chickens fed suboptimal level of dietary methionine. The experimental design was a 2 × 2 factorial arrangement of treatments evaluating two levels of betaine supplementation (0 and 960 g betaine/t of feed) without or with coccidia challenge. Each treatment was fed to 8 cages of 8 male broilers (Ross 308) for 1 to 21d. On d 14, birds in the 2 challenged groups received mixed inocula of Eimeria species from a recent field isolate, containing approximately 180,000 E. acervulina, 6,000 E. maxima, and 18,000 E. tenella oocysts. At 21d, digesta from the terminal ileum was collected for the determination of dry matter, energy, nitrogen, amino acids, starch, fat, and ash digestibilities. Lesion scores in the different segments of the small intestine were also measured on d 21. Performance and nutrient digestibility data were analyzed by two-way ANOVA. Lesion score data were analyzed using Pearson chi-square test to identify significant differences between treatments. Orthogonal polynomial contrasts were used to assess the significance of linear or quadratic models to describe the response in the dependent variable to total lesion scores. Coccidia challenge reduced (P < 0.0001) the weight gain and feed intake, and increased (P < 0.0001) the feed conversion ratio. Betaine supplementation had no effect (P > 0.05) on the weight gain or feed intake, but lowered (P < 0.05) the feed conversion ratio. No interaction (P > 0.05) between coccidia challenge and betaine supplementation was observed for performance parameters. Betaine supplementation increased (P < 0.05) the digestibility of dry matter, nitrogen, energy, fat, and amino acids only in birds challenged with coccidia as indicated by the significant interaction (P < 0.0001) between betaine supplementation and coccidia challenge. The main effect of coccidia challenge reduced (P < 0.05) starch digestibility. Betaine supplementation improved (P < 0.05) starch digestibility regardless of the coccidia challenge. For each unit increase in the total lesion score, there was a linear (P < 0.001) decrease in digestibility of mean amino acids, starch, and fat by 3.8, 3.4 and 16%, respectively. Increasing total lesion scores resulted in a quadratic (P < 0.05) decrease in dry matter digestibility and ileal digestible energy. No lesions were found in the intestine or ceca of the unchallenged treatments. In the challenged treatments, betaine supplementation reduced (P < 0.01) the lesion scores at the duodenum, lower jejunum, and total lesion scores compared to the treatment without supplements. In conclusion, coccidia challenge lowered the digestibility of energy and nutrients and increased the feed conversion ratio of broilers. However, betaine supplementation reduced the impact of coccidia challenge and positively affected nutrient digestibility and the feed conversion ratio.

The effect of mitochondrial ATP-sensitive potassium channels on apoptosis of chick embryo cecal cells by Eimeria tenella

The objective of this study was to investigate the effect of mitochondrial ATP-sensitive potassium (mitoKATP) channels on apoptosis induced by Eimeria tenella. At 24, 48, 72, 96 and 120 h after Eimeria tenella infection, TUNEL assays and translation of phosphatidyl serines to the host cell plasma membrane surface showed that diazoxide-treated chick embryo cecal cells underwent less apoptosis (P <0.05), while light microscopy showed that infection rates of treated cells were higher (P <0.01) than untreated cells. Caspase 9 and caspase 3 of infected cells were activated less (P <0.01) in diazoxide-treated cells than untreated cells. These results indicate that opening mitoKATP channels can protect chick embryo cecal cells from mitochondria-dependent apoptosis induced by Eimeria tenella by inhibiting activations of caspase 9 and caspase 3.

Aminopeptidase N1 (EtAPN1), an M1 metalloprotease of the apicomplexan parasite Eimeria tenella, participates in parasite development

Aminopeptidases N are metalloproteases of the M1 family that have been reported in numerous apicomplexan parasites, including Plasmodium, Toxoplasma, Cryptosporidium, and Eimeria. While investigating the potency of aminopeptidases as therapeutic targets against coccidiosis, one of the most important avian diseases caused by the genus Eimeria, we identified and characterized Eimeria tenella aminopeptidase N1 (EtAPN1). Its inhibition by bestatin and amastatin, as well as its reactivation by divalent ions, is typical of zinc-dependent metalloproteases. EtAPN1 shared a similar sequence, three-dimensional structure, and substrate specificity and similar kinetic parameters with A-M1 from Plasmodium falciparum (PfA-M1), a validated target in the treatment of malaria. EtAPN1 is synthesized as a 120-kDa precursor and cleaved into 96-, 68-, and 38-kDa forms during sporulation. Further, immunolocalization assays revealed that, similar to PfA-M1, EtAPN1 is present during the intracellular life cycle stages in both the parasite cytoplasm and the parasite nucleus. The present results support the hypothesis of a conserved role between the two aminopeptidases, and we suggest that EtAPN1 might be a valuable target for anticoccidiosis drugs.